A number of elements drawn from several aspects of Star Trek history come together to explain how Klingons lost their forehead ridges for the better part of a generation in "Divergence," the conclusion of a two-parter beginning with "Affliction."

As explained in the last production report, the writing staff has devised a scenario to explain the Klingon discrepancy that takes into account all previously established canon. "Divergence" was specifically written by Judith and Garfield Reeves-Stevens, two prominent experts on Trek lore.

To summarize the story without giving too much away, Enterprise is on a quest to learn why Phlox was kidnapped and where he was taken (per the last episode). As the show opens, however, the crew must grapple with sabotage to the ship's systems which threatens to blow up the warp reactor. After resolving that situation with the help of Captain Erika Hernandez and the newly launched Columbia NX-02, Archer learns that Phlox is located deep in Klingon territory, so the two ships take a dangerous turn together in that direction. Meanwhile Phlox decides to cooperate in addressing the affliction which is ravaging the Klingon population. Like in the previous episode, we will get to see the beginnings of the new breed of Klingon, the smooth-headed kind seen in the original Captain Kirk era.

John Schuck continues on from the previous segment as "Antaak" — the Klingon scientist Phlox works with — as do Ada Maris as "Captain Hernandez" and Eric Pierpoint as the shady "Harris." Also carrying over from "Affliction" is James Avery as the Klingon "General K'Vagh." Actor/comedian Avery is best known as the patriarch "Philip Banks" on The Fresh Prince of Bel-Air, but has a long and diverse resumé of credits which includes voice work on such shows as Teenage Mutant Ninja Turtles. Terrell Tilford, another character actor, also returns as "Marab," a smooth-headed "Type Two" Klingon.

Joining the guest list in "Divergence" is Wayne Grace as Klingon Fleet Admiral "Krell." Grace has been a Klingon before, as "Governor Torak" in Star Trek: The Next Generation's "Aquiel," and he also lent his voice to the "Star Trek: Klingon Academy" video game; he was also a Cardassian in Star Trek: Deep Space Nine's "Wrongs Darker Than Death or Night." A female "Type Two" Klingon, the treacherous "Laneth," is played by Kristin Bauer, a Trek newcomer. Bauer was seen in Dark Angel as "Lydia Meyerson," along with a variety of other roles.

Production on this installment started Tuesday, December 14, and was literally cut in half by the two-week holiday hiatus. The first four days of the schedule saw shooting on standing ship sets such as the Ready Room, Corridors, Brig, Engineering, and a slightly redressed Bridge to represent Columbia. On Thursday John Billingsley spent the entire day in the Klingon Laboratory set with Schuck and Avery, while the rest of the principal cast occupied the adjacent soundstages in second-unit photography for "United." The first day of the schedule, Tuesday, wrapped early — 5:00 p.m.— so the cast and crew could retreat to the studio Commissary for a holiday party hosted by Scott Bakula.

The first day back, January 3, was relatively light. After spending a couple of hours shooting Bridge scenes for "Divergence," the rest of the day was spent in second-unit work for "Babel One" and "United," under the direction of visual effects supervisor Dan Curry. Tuesday morning, Pierpoint — whose character is seen only on monitors in this segment — did all his shots against a one-wall set. The same day Grace did all his scenes on two sets, the Bridge and Cabin of a Klingon Battlecruiser, during which he got to learn the delights of eating gagh. The rest of Tuesday and Wednesday played out with more scenes in the Klingon Lab, a Klingon Barracks set, and the Enterprise Sickbay. Needless to say, the Makeup department had quite a task in keeping up with all the various Klingon looks demanded by the script — different stages of illness and forehead ridgieness — and even had a prosthetic to do for one of our human characters.

Principal photography was scheduled for seven days, as normal, but there was an elaborate sequence that was pushed off into B-unit production on Thursday (Jan. 6), overlapping with the beginning of the next episode. That sequence involves Columbia's efforts to help Enterprise resolve its sabotage crisis. The NX-01 cannot drop out of warp, so in an unprecedented maneuver, an attempt is made to transfer a crew member from Columbia to Enterprise along a cable strung between the launch bays of each ship ... at Warp 5. (The transporter can't operate at warp, and docking is impossible.) A great deal of intricate shooting took place on the Launchbay set — dressed first as Enterprise and then as Columbia — including some upside-down camera angles. A cable rigging was devised by the special effects department that included a "teeter-totter" attachment for the personnel transfer. Greenscreens were used in various places where digital images will be inserted later, such as the underbelly of the other ship seen from inside the launchbay. Connor Trinneer and Dominic Keating took part in the sequence wearing EV suits, along with stuntman Shawn Crowder.

The episode was helmed by Dave Barrett, a first-time director on Enterprise. As mentioned, the script was written by the Reeves-Stevens couple, who since joining the staff this season have been responsible for "The Forge," "Observer Effect" (airing next week) and "United."

"Divergence" is tentatively set to air February 25. Updates will be posted in Episode Detail.

Per the current airdate schedule from UPN (which has not changed since the last production report), there will be seven new episodes in a row starting this Friday with "Daedalus." Next week's "Observer Effect," another stand-alone segment, will be followed by the three-part Romulan/Andorian arc, which will then be followed by the Klingon two-parter. After several reruns, there will be six new episodes remaining in the season. As always, airdate information is subject to change.